Table 2:
Summary of the literature investigating the relationship between air pollutants and spontaneous abortion.
| Reference | Location | Study design | Study population (SAB/confirmed pregnancies) | Outcome definition | Exposure | Exposure assessment | Major findings | Notes |
|---|---|---|---|---|---|---|---|---|
| Dastoorpoor et al. (27) | Iran | Time series | 1334/49,173 Births | Fetal loss ≤20 weeks’ gestation | PM10, CO, NO, NO2, SO2, O3 | Khuzestan Province EPA daily measurements | Rate ratio (95% Cl) per 10 μg/m3 increase: Cumulative Lag (Lag 0 to 14) PM10:1.01 (1.00,1.02) CO: 0.28 (0.07, 1.08) NO: 1.00(0.84,1.20) NO2: 1.10(0.99,1.23) SO2: 1.01 (0.96, 1.07) O3: 1.00(0.98,1.10) Lag 0: SO2: 1.01 (1.00, 1.02) |
Adjustments for trend, seasonality, temperature, relative humidity, weekdays, holidays |
| Di Caula and Bilancia (28) | Italy | Time series | 984 Cases | Fetal loss within 180 days of gestation | PM10, NO2) O3 | Regional environmental agency average monthly levels | ARR (95% Cl) per 10 μg/m3 increase: PM10:1.20 (1.08,1.34) NO2: 0.96 (0.87, 1.05) 03:1.34 (1.26,1.42) |
Adjustments for temperature and humidity |
| Guimarães et al. (29) | São Paulo, Brazil | Cross-sectional | 199/4296 | Fetal loss <20 weeks’ gestation | Heavy metals, organochlorine compounds | Questionnaire and interview | AOR (95% Cl): Area la: 1.04 (0.66,1.65) Area 2b: 1.06 (0.64, 1.74) Area 3c: 1.55 (0.98, 2.46) Area 4d: 1.12 (0.69, 1.81) Area 5: Control |
Adjustments for time of residence in region, age group, education, marital status, family income, current and past occupational exposure, alcohol and tobacco use, prenatal care; a: Industrial and petrochemical landfill b: Industrial center c: Chemical and pesticides landfills d: Chemical industry and port |
| Hafez etal. (30) | Egypt | Cross-sectional | 565/1934 | Did not report definition | TDC, SDC, RDC | Questionnaire | AOR: TDC (Mppcf): 33.04 SDC (μig/m3): 0.03 RDC (μg/m3): 0.72 (p<0.05) |
Adjustments for education, lead concentration, occupation, SES, smoking, RDC, SDC; No Cl reported |
| Hou etal. (31) | Tianjin, China | Case-control | 959 Cases 959 Controls | Evidence of fetal pole ≥6 mm within intra-uterine gestationalsac, but absence of heartbeat | SO2, TSP, PM10, NO2 | Tianjin air monitoring stations daily and monthly concentrations | AOR fetal loss within 14 weeks (95% Cl): SO2:19.76 (2.34,166.71) TSP: 2.04 (1.01, 4.13) |
Only SO2 and TSP selected for logistic regression model Adjustments for maternal age, gravidity, parity, gestational age |
| Mohorovic eta 1.(32) | Croatia | Case-control | 3/138 vs. 6/122 | Did not report definition | SO2 | Maternal methemoglobin | Frequencies of SAB lower in clean period compared to dirty period (p<0.05) | Frequencies lower in the control compared to the “exposure” |
| Moridi et al. (33) | Tehran, Iran | Case-control | 148 Cases 148 Controls | Fetal loss <14 weeks’ gestation | PM10, CO, NO2, O3,SO2 | Tehran air quality control company annual average concentration | AOR (95% Cl) cases vs. controls: PM10: 1.01 (1.00, 1.02) CO: 1.95 (1.50, 2.55) NO2:1.04 (1.02,1.05) O3:1.10 (1.06,1.13) |
S02p value > 0.05; Adjustments for maternal and paternal age, cigarette smoke exposure, occupation, pre-pregnancy BMI, other demographic parameters |
| Samaraweera and Abeysena (34) | Sri Lanka | Case-control | 230/731 | Confirmed diagnosis of partial or full expulsion of fetus ≤28 weeks | Cooking smoke | Self-report | AOR (95% Cl) exposure to smoke generated by cooking in a kitchen without a chimney: Second trimester: 3.83 (1.50, 9.90) | Adjustments for maternal age, pre-pregnancy BMI, parity, previous abortions, education, employment, walking/standing/sitting/sleeping per day, stressful life events, medication, passive smoke, cooking smoke |
| Wuetal. (35) | Tianjin, China | Case-control | 81 Cases 81 Controls | Confirmed dead in-utero fetus <14 weeks’ gestation | PAH | Interview, aborted tissue, maternal blood draw (102 subjects) | AOR of missed abortion (95% Cl): 1.35(1.11,1.64) Maternal blood BaP-DNA level per adduct/108 nucleotides |
Adjustments for maternal education and household income |
| Perin et al. (36) | São Paulo, Brazil | Retrospective cohort | 34/177 IVF/ET patients, 18/354 Control patients | First trimester loss: loss in first 12 weeks | PM10 | São Paulo EPA (CETESB) daily levels | AOR Women exposed to >56.72 μg/m3 vs. ≤56.72 ng/m3: 2.585 (p = 0.00) | OR for women exposed to the Q4 period (>56.72 μg/m3) during the follicular phase of conception compared to women exposed to Q1–Q3 periods (0, 56.72 μg/m3). |
| Perin etal. (37) | São Paulo, Brazil | Retrospective cohort | 45/348 IVF/ET patients | Pregnancy diagnosed with pos. serum p”hCG that failed to reach the 12 weeks gestation | PM10 | São Paulo EPA (CETESB) daily levels | AOR (95% Cl) Women exposed to >56.72 μg/m3 vs. ≤56.72 (μg/m3: 5.05(1.04,25.51) | Adjustments for level of PM10 |
| Green etal. (38) | CA, USA | Prospective cohort | 499/4979 | Pregnancy ending ≤20 weeks | NO2, AADT | California Air Resources Board and Spatial Variation | AOR (95% Cl): 1.18 (0.87,1.60) for top 90th Percentile of AADT vs. bottom 75th percentile AADT |
Adjustments for maternal age, race/ethnicity, SES, cigarette smoke exposure, employment status, stressful life events |
| Haetal. (39) | United States | Prospective cohort | 97/246 | Neg. pregnancy test after pos. test, clinically confirmed loss, or onset of menstruation | PM2.5, PM10, CO, NO2, O3,SO2 | Community multiscale air quality models | HR for IQR increase: Entire pregnancy: PM2.5:1.13 (1.03,1.24) PM10: 1.02 (0.99, 1.06) CO: 1.00 (1.00, 1.00) NO2: 1.03(0.98,1.08) O3: 1.12(1.07,1.17) SO2: 1.01 (0.77, 1.34) |
Adjustments for season study site, maternal age, race, education, income, parity condition on gravidity, early pregnancy caffeine intake, BMI, early pregnancy adherence to multivitamin intake, maternal blood cotinine level, paternal blood cotinine level |
SAB, Spontaneous abortion; PM2.5, particulate matter ≤ 2.5 μm; PM10, particulate matter ≤ 10 μm; CO, carbon monoxide; NO2, nitrogen dioxide; SO2, sulfur dioxide; O3, ozone; TDC, total dust count; SDC, suspended dust concentration; RDC, respirable dust concentration; TSP, total suspended particles; H2S, hydrogen sulfide; AADT, annual average daily traffic; IVF, in vitro fertilization; ET, embryo transfer; AOR, adjusted odds ratio; COR, crude odds ratio; ARR, adjusted risk ratio; HR, hazard ratio; IQR, interquartile range; BMI, body mass index; CI, confidence intervals. Values in bold indicate significant confidence intervals.